Method and apparatus for tensile testing and rethreading optical fiber during fiber draw

ABSTRACT

A method and apparatus for automatic threading and winding of optical fiber onto various components in a fiber draw system, as well as methods and apparatus for conducting online tensile screening of optical fiber at high speeds. In a preferred embodiment, the fiber is tensile tested during fiber draw and wound directly onto a shipping spool to be shipped to a customer. The tensile stress can be imparted to the fiber during the draw process by feeding the fiber through a screener capstan, which works in conjunction with another capstan to impart the desired tensile stress to the fiber during the draw process. Another aspect is a method and apparatus for threading or rethreading of a moving length of fiber through a fiber draw or fiber testing process, in which fiber is wound onto a spool, comprising activating an aspirator to obtain the fiber at a first location and moving said aspirator in at least two dimensions to thereby move the fiber to a second location and thread the fiber through or onto at least one component in the fiber draw or testing process.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This is application claims the benefit of U.S. Provisional PatentApplication Serial No. 60/173,401 filed on Dec. 28, 1999, the content ofwhich is relied upon and incorporated herein by reference in itsentirety, and the benefit of priority under 35 U.S.C. § 120 is herebyclaimed.

FIELD OF THE INVENTION

[0002] The present invention relates to a method and apparatus forautomatic threading and winding of optical fiber onto various componentsin a fiber draw system. The invention further relates to methods andapparatus for conducting online tensile screening of optical fiber athigh speeds and winding of the screened optical fiber directly ontooptical fiber shipping spools.

BACKGROUND OF INTRODUCTION

[0003] Optical waveguide fibers (optical fibers) are a well-knowntransmission medium used in optical communication systems. Fiber drawmanufacturing techniques are known wherein the optical fiber is drawnfrom an optical fiber preform and wound onto a spool. In the past, thedrawing of optical fiber has typically involved winding of the fiberonto bulk spools that may hold up to 400 km of fiber. The bulk spool isthen typically manually transported to an off-line rewinding machinethat is threaded manually by an operator. The off-line machine rewindsfiber from the bulk spool to a plurality of smaller shipping spools.Prior to or during the transfer of the fiber from the bulk spool to thesmaller shipping spools, various tests are conducted on the fiber. Forexample, the same machine used to wind the fiber from the bulk spool tothe shipping spool is also commonly employed to apply a predeterminedminimum level of stress (typically 100 kpsi) to the fiber to make surethe fiber meets the minimum strength requirements. This application ofstress is commonly called screening or proof testing. The machine stopswinding to the shipping spool when screening breaks occur, and theoperator must then manually rethread the machine again and begin windingthe fiber onto a new spool.

[0004] It would be desirable to conduct tensile strength proof testingon the fiber during the fiber draw process, before it is wound onto astorage spool, which preferably is a shipping spool. However, with thehigh draw speeds (e.g. greater than 20-25 m/s) employed in some oftoday's fiber manufacturing operations, such online proof testing hasnot been achievable. For one thing, online screening would increase thenumber of fiber breaks in the fiber at the draw, due to the addedtensile stress applied to the fiber to proof test it. In addition,because the fiber draw process cannot be stopped, there would be a greatdeal of lost fiber while the operator rethreaded the online tensilescreening equipment. Of course at the higher draw speeds (e.g. greaterthan 20 m/s) employed in many of today's fiber draw processes, the fiberbeing threaded would somehow also have to keep up with the length offiber being fed by the fiber draw process. Also, because of the timeinvolved with threading conventional tensile testing apparatus, usingconventional techniques a great deal of fiber would be lost during therethreading operation. As a result, manufacturers have thus far insteadhad to resort to manufacturing processes wherein they draw the fiber atlower draw tensions onto relatively large (e.g. can store 400 km ormore) bulk spools. These fiber on these bulk spools is then proof testedoff-line, during or prior to its being wound onto smaller shippingspools.

SUMMARY OF THE INVENTION

[0005] One aspect of the present invention relates to a method oftensile proof testing an optical fiber during a fiber draw process,comprising pulling a length of optical fiber from an optical fiberpreform at a fiber draw speed greater than 20 m/s, imparting a desiredtensile stress to said fiber to thereby test the strength of said fiberand subsequent to said imparting a tensile stress, winding said fiberonto a spool. The tensile stress applied to the fiber preferably isequal to a desired proof testing force. Preferably the desired tensilestress is greater than about 80 psi, and more preferably the desiredtensile stress is greater than about 95 psi.

[0006] In a preferred embodiment, the fiber is wound directly onto ashipping spool to be shipped to a customer. Preferably the shippingspool is not capable of holding more than 150 km, more preferably notmore than 100 km, and most preferably not more than about 75 km ofoptical fiber. Such shipping spools can then be shipped directly to acustomer without having to be rewound onto smaller spools. Preferably,the shipping spool is one which enables access to both ends of saidfiber on said spool, and the fiber is wound onto said shipping spool ina manner which enables both ends of said fiber to be accessed while saidfiber is stored on said spool. In this way, optical properties testingand other forms of testing can be conducted on the fiber while stored onthe spool, without having to remove the fiber from the spool. Forexample, the fiber can be tested by a testing method which involvesconnecting one end of said fiber on the spool to a light source,launching light from the light source through the fiber, and evaluatingthe properties of the light at the other end of the fiber. Examples ofsuch tests include optical time domain reflectometry (OTDR), which isused to measure the amount of dispersion per unit length in the fiber,as well as dispersion geometry and polarization mode dispersion.

[0007] The tensile stress can be imparted to the fiber during the drawprocess by feeding the fiber through a screener capstan, which works inconjunction with another capstan to impart the desired tensile stress tothe fiber during the draw process. For example, the screener capstan maybe located downstream of another capstan and rotated at a highercircumferential speed than the other capstan to thereby pull the fiberand impart a desired tensile stress. Preferably, the fiber tensionbetween the two capstans is monitored during the draw process and thespeed of the screener capstan adjusted in response to the monitoredtension, to thereby constantly maintain a desired tensile screeningforce or range of forces. For example, the tension in the fiber can bemonitored via a load cell (for example, which may be located between thetwo capstans) operatively connected to a pulley, which in turn contactsthe fiber. A computer can be used to monitor the tension in said fibervia the load cell and adjust the speed of the screener capstanaccordingly. Alternatively, other methods could be employed to impartthe desired amount of tensile stress to the fiber during the drawprocess. For example, such stress could be applied using a weight whichis applied onto a pulley around which the fiber travels during the drawprocess. Alternatively, the fiber could be wound around two capstanswhich are mechanically linked so that one of the capstan travels at ahigher circumferential speed than the other capstan. A still furtheralternative would be to have the fiber travel around a pulley having twodifferent adjacent fiber track channels, each fiber track channel havingdifferent circumferences, the difference in circumferences beingselected to provide a desired tensile force onto the fiber as it passesthrough the two track channels of the pulley.

[0008] Another aspect of the invention relates to a method and apparatusfor threading or rethreading of a moving length of fiber through a fiberdraw or fiber testing process, in which fiber is wound onto a spool,comprising activating an aspirator to obtain the fiber at a firstlocation and moving said aspirator in at least two dimensions to therebymove the fiber to a second location and thread the fiber through or ontoat least one component in the fiber draw or testing process. The movinglength of fiber can be, for example, a moving length of fiber in a fiberdraw process or an off-line fiber screening process. In a preferredembodiment, the aspirator is moved to guide the fiber onto at least oneguide pulley, after which the fiber is moved proximate to the windingspool, where it is engaged and the fiber is wound upon the spool. Forexample, the fiber length may be engaged by a snagger tooth or otherdevice capable of grabbing the fiber on the storage spool. Immediatelyafter the fiber is engaged by the rotating spool, the fiber is cut toseparate the fiber from the aspirator. The guide pulley in this case andthe fiber storage spool then traverses with respect to one another towind the fiber onto the spool.

[0009] In another embodiment, the method further comprises orienting atleast a first, second, and third pulley so that, when the aspiratormoves said fiber to said second location, the pulleys are disposed alongthe length of said fiber and on alternating sides of said desired fiber.The second pulley is then moved across the path of the fiber to therebyretain the fiber in contact with the first, second, and third pulleys,thereby causing the fiber to move in a serpentine path.

[0010] In still another embodiment, the aspirator is used together withanother, separate fiber guiding device, to guide the fiber through atleast one component in a fiber winding system. For example, a mechanicalguide finger assembly can be used to engage a portion of the fiber,between the source of the fiber and the aspirator. The guide finger canthen bend and move the path of the moving optical fiber and therebyguide the fiber onto or through the component to be threaded.Preferably, the guide finger is a cylindrical member over which thefiber may travel freely and continue to be collected by the aspirator.Such a guide member could be in the form of a hook or J-shaped member,or more preferably is a cylindrical tube or rod, which may or may not berotatable around its axis to facilitate free travel of the fiber overthe guide finger.

[0011] Another aspect of the invention relates to an apparatus fordrawing and winding fiber onto a spool, and prooftesting the fiber afterdrawing of the fiber but prior to the fiber being wound onto the spool.The apparatus includes a furnace for softening an optical fiber preformsufficiently that a fiber can be drawn therefrom; a first capstan ofother fiber drawing device designed to draw fiber from the preform at arate exceeding 20 m/s, and preferably exceeding 25 m/s, and aprooftesting device. The prooftesting device preferably includes thefirst capstan device (also known as the tractor capstan assembly)located downstream of the furnace including at least one wheel and amotor for driving the wheel at a first circumferential speed, and asecond capstan assembly including at least one wheel and a servo motorfor driving the wheel at a second circumferential speed so that thedifference between the first and second circumferential speeds creates adesired proof testing tensile stress which is applied to the fiber. Aload cell is preferably operatively connected to the fiber (e.g.,between the two capstans) for monitoring tension in the fiber. Acomputer control is provided for receiving input from the load cell andadjusting the speed of the first or second capstan assemblies to aid inmaintaining a uniform tensile stress or within a desired range oftensile stress.

[0012] The automatic rewinding methods and apparatus described hereinenable a number of advantages over the prior art. For one thing, byusing the aspirator and guide finger in the manner and method disclosedherein to rethread the optical fiber through various components of thefiber winding system, fiber can continuously be removed and discardedfrom the manufacturing process as it is simultaneously being threadedthrough the system. Consequently, the supply of fiber does not have tobe stopped in order to rewind or rethread the system. Using thetechniques disclosed herein, an entire on-line winding system, includingan on-line prooftesting section, can be rewound in less than 10 seconds.In fact, using the methods and apparatus disclosed herein, rewinding ofthe entire fiber winding system, including an on-line fiber tensilestrength screening device, has been achieved on line during aexperimental fiber draw operation in less than 7 seconds. This includesproviding a fresh shipping spool, guiding the fiber into windingengagement with the new spool, and beginning winding of the fiber to thenew spool. Because the present invention enables rethreading of thefiber winding system in such a short period of time, on-line prooftesting can be achieved, even at draw speed of 25-30 m/sec. or more,without having to worry about losing a significant amount of fiber.

[0013] On-line screening of the fiber in turn enables the fiber to bewound directly onto shipping spools, rather than large bulk storagespools, thus greatly reducing or even totally eliminating the costsassociated with the previous method of drawing the fiber onto a bulkspool, conducting off-line proof-testing, and then winding the fiberonto shipping spools.

[0014] By winding the fiber onto a spool capable of providing access toboth ends of the fiber, and by selecting the length of fiber wound onthe spool to be short enough (e.g. less than 150 km, more preferablyless than 100 km, and most preferably less than 75 km), any opticalmeasurements that are to be conducted on the fiber can be done while thefiber is stored on the spool. Consequently, the fiber can be drawn froman optical fiber preform at high speed (e.g., greater than 20, morepreferably greater than 25, and most preferably greater than 30 m/s),tensile tested during the fiber draw process, and then wound onto afiber storage spool. The fiber could then be tested offline while storedon the fiber storage spool for any additional (e.g. other optical)desired measurements, and then shipped directly to a customer (e.g. afiber optic cable company who then cables various strands of opticalfiber into an optical fiber cable) without ever having to rewind thefiber onto a different spool.

[0015] Also, because the automatic rewinding methods and apparatusdisclosed herein greatly facilitate and speed up the fiber rewindingprocess, fiber can now be selectively removed during the fiber drawoperation if desired without the loss of significant amounts of fiber.For example, if fiber is detected that has a diameter (e.g. fiber orcoating diameter) that is out of specification, the defective fiber canbe cut, and the bad fiber allowed to be collected and discarded into theaspirator, until good (i.e., in specification) fiber is again detected,after which time the fiber is wound onto the ondraw sceener and onto afiber storage spool.

[0016] Additional features and advantages of the invention will be setforth in the detailed description which follows, and in part will bereadily apparent to those skilled in the art from that description orrecognized by practicing the invention as described herein, includingthe detailed description which follows, the claims, as well as theappended drawings.

[0017] It is to be understood that both the foregoing generaldescription and the following detailed description are merely exemplaryof the invention, and are intended to provide an overview or frameworkfor understanding the nature and character of the invention as it isclaimed. The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated in and constitute apart of this specification. The drawings illustrate various embodimentsof the invention, and together with the description serve to explain theprinciples and operation of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]FIG. 1 is a perspective view of a preferred embodiment of awinding apparatus according to the present invention.

[0019]FIG. 2 is an enlarged perspective view of the screener section ofthe winding apparatus of FIG. 1.

[0020]FIG. 3 is an enlarged perspective view of the spool windingsection of the winding apparatus of FIG. 1.

[0021] FIGS. 4A-4E are top plan views of the winding apparatus of FIG.1, illustrating the optical fiber being threaded onto the screenercapstan.

[0022] FIGS. 5A-5C are top plan views of the winding apparatus of FIG.1, illustrating threading of the optical fiber through the windersection.

[0023]FIG. 6 illustrates a preferred fiber storage spool for use inaccordance with the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0024]FIGS. 1, 2, and 3 illustrate a preferred optical fiber windingsystem 10 in accordance with the present invention, wherein opticalfiber 8 is drawn directly from an optical fiber preform or draw blank inan optical fiber draw process. As illustrated in FIG. 1, the majorcomponents of the system include a screening section 12, where the fiberis proof tested, and a winding section 14, where the fiber is wound ontoa fiber storage spool 15.

[0025] The fiber is mechanically stressed a desired amount (i.e., prooftested) while traveling through screener section 12 which is illustratedin FIGS. 1 and 2. The fiber is then wrapped directly onto spool 15 infiber winder section 14, illustrated in FIGS. 1 and 3. Spool 15preferably is a shipping spool which is either to be shipped directly toa customer, which may be a purchaser of optical fiber and/or a cablemanufacturing plant to be cabled directly without having to be respooledonto another fiber storage spool. In this way, from the time the fiberis first drawn into an optical fiber until the fiber is cabled into anoptical fiber cable, the fiber may be stored on a single storage spool,without having to endure transfer to successive storage spools, betweenthe time at which the fiber is manufactured and the time the fiber isshipped to a customer, to enable various testing procedures.

[0026] A preferred optical fiber storage spool which may be used inaccordance with the invention is illustrated in FIGS. 6A and 6B, whichshow, respectively, side and bottom views of preferred shipping spool15. As shown in FIG. 6, the spool 15 includes a primary barrel portion60, and lead meter barrel portion 62, and an angled slot 64 throughwhich fiber can be fed during the winding process from the lead meterportion 64 to the primary barrel portion 62, or vice versa depending ondesired winding techniques. Such spools are described further, forexample, in U.S. patent Ser. No. 09/438,112, filed Nov. 10, 1999, titledSystem and Method for Providing Under-Wrap Access to Optical Fiber WoundOnto Spools, which claims the benefit of U.S. Provisional ApplicationNo. 60/114,516, filed Dec. 30, 1998, and No. 60/115,540, filed Jan. 12,1999, the specification of which is hereby incorporated by reference. Ina preferred embodiment of the invention, the fiber is fed onto spool 15beginning at lead meter barrel portion 62. When a desired amount offiber has been stored on the lead meter portion 62, the fiber is thenfed through the slot and onto primary barrel portion 60, and a desiredamount of fiber is then wound onto primary barrel portion 60. Once thespool is full and/or a desired amount of fiber is contained within theprimary barrel portion 60, the fiber is cut, e.g. between the fiberwinding system and the fiber screening system and rotating turret 40indexes 180 degrees to provide another empty storage spool 15 onto whichfiber can again be wound. The previously filled spool is then removed,and an empty spool loaded in its place, and so forth, so that when thenewly provided empty spool is filled, the next spool will ready, and soforth. One reason shipping spool 15 is preferred is that fiber may bestored on spool 15 in a manner which enables access to both ends of thefiber. Because the spool enables access to both ends of the fiber,optical and other testing can be conducted on the fiber which is storedon spool 15 after the fiber draw and winding process, without having toremove the entire length of fiber from the spool or rethread the fiberonto a different spool.

[0027] The system also includes aspirator 16, illustrated in FIGS. 1 and2, which is used to remove scrap fiber from the process as well as tofacilitate automated threading of the fiber onto the various componentsof the system at the beginning of the draw operation or after a fiberbreak, of after the fiber is intentionally cut, as will be furtherdescribed below. As can be seen in FIGS. 1 and 2, aspirator 16 consistsbasically of a cylindrical tube such as a vacuum hose, and is movablyattached to vertical support member 17 along which the aspirator can bemoved in an upward or downward path. Such aspirators can, for example,use compressed air to provide the sucking force needed to suck fiberinto aspirator 16. Preferably the compressed air has a velocity which ishigh enough to provide sufficient tension to capture and controlmovement of the fiber throughout the winding system as it is beingrethreaded, as well as to convey away any scrap fiber. Vertical supportmember 17 is in turn movably mounted on transverse support member 18,which in turn is movably mounted on main aspirator support frame 19. Inthis way the aspirator can be moved in 3 dimensions, e.g., the aspiratorcan be moved closer to or further away from screener section 12 by thesliding of transverse support member 18 along the main support frame 19.The aspirator 16 can also be moved transverse to the main support frame(toward or away from the back of the machine system, i.e., parallel tothe axis of the indexing spool winding 40) by sliding of the verticalsuport member 17 along transverse support member 18.

[0028] Operation of the fiber winding system in accordance with thepresent invention is preferably controlled via a computer controlsystem, which may be programmed to respond to various inputs, which maybe either automatically sent from the winding system or manuallyinputted by a machine operator.

[0029] During the fiber draw operation, an optical fiber draw blank(also known as an optical fiber preform) is mounted in a draw furnace(not shown), and the temperature in the furnace is raised to atemperature suitable for drawing optical fiber from the preform. As canbe seen in FIG. 2, screener section 12 includes a pair of capstanassemblies 20 and 24, each of which consist of a large capstan wheel anda belt which is in engagement with a portion of the circumference of thelarge capstan wheel. The belt is also supported by three smaller wheels,which are positioned so that the belt is held firmly against the largercapstan wheels. As used generally herein, capstan refers to such capstanassemblies as are illustrated in FIG. 2, although alternative capstanassemblies could also be employed without detracting from the spirit ofthe invention. Optical fiber 8 is pulled from the drawblank during thefiber draw operation by belted capstan 20, also known as and referred toherein as the tractor capstan, illustrated in FIG. 2. The speed ofbelted capstan 20 can be controlled by suitable control means to achievea desired speed for drawing the fiber.

[0030] As shown in FIG. 2, in the embodiment illustrated, the fiberexits tractor capstan 20 and wraps 180 degrees around turnaround pulley22. Turnaround pulley 22 has a recessed groove around its peripherywithin which the fiber 8 is retained. Turnaround pulley 22 is connectedto a load cell which monitors the amount of tension applied onto theturnaround pulley by the passing fiber, and thus monitors the amount oftension being imparted to the fiber. From turnaround pulley 22, thefiber enters belted screener capstan 24. In the embodiment illustratedthe screener capstan 24 is electronically “slaved” to tractor capstan 20so that at all times it rotates slightly faster than tractor capstan 20.The speed differential between screener capstan 24 and tractor capstan20 is maintained at a magnitude, which causes a desired amount of strainwithin the fiber. The strain imparted to the fiber is directlyproportional to the tensile stress in the fiber. Any tension present inthe fiber prior to entering the tractor capstan 20 is added to thetension caused by the differential speed of the two capstans 20 and 24.Depending on the speed at which the fiber is being drawn, the incomingtension during a normal blank run can vary by as much as 30 kpsi.Consequently, in a preferred embodiment, feedback from the load cell ofthe turnaround pulley 22 is used to adjust the differential speed of thescreening capstan 24 so that a sufficient screening tension ismaintained consistently throughout drawing of the entire optical fiberblank into optical fiber.

[0031] During the fiber draw process, fiber exits screener capstan 24 inscreening section 12 and proceeds to winding section 14, which isillustrated in FIG. 3. In the embodiment illustrated, the fiber leavesscreening capstan 24 in FIG. 2 at an angle which is approximately 30degrees to the manufacturing plant floor, and proceeds to the windingsection 14 illustrated in FIG. 3. At winding section 14, the fiber 8 iswound through four process pulleys 30 a-30 d before being wound ontofiber storage spool 15. In the embodiment illustrated, the first threeprocess pulleys 30 a-30 c are disposed substantially within the sameplane as the incoming fiber, in this case 30 degrees relative to theplant floor. The fiber wraps 90 degrees around the first pulley 30 a andthen 180 degrees around second pulley 30 b, which is a dancer pulley.Dancer pulley 30 b is attached to a pivot arm 32. Such dancer pulleymechanisms are described further, for example, in U.S. patentapplication Ser. No. 09/390,866, filed September 7, titled PassiveTension Regulator, the specification of which is hereby incorporated byreference.

[0032] From dancer pulley 30 b, the fiber wraps 90 degrees around thirdpulley 30 c and then around fourth pulley 30 d, whose axis of rotationis perpendicular to that of the first three pulleys 30 a-30 c. The fiberwraps approximately 45 degrees around the fourth pulley 30 d and thencontinues to the take up spool 15. Pulley 30 d is oriented to redirectand guide fiber 8 onto take up spool 15. The third and fourth pulleys 30c and 30 d are both mounted on traversing carriage 34 which traverseback and forth parallel to the axis of the take up spool 15 during thefiber winding operation to result in uniform winding of the fiber ontospool 15. Carriage 34 moves back and forth along a support bar (notshown), reciprocating parallel to the axis of spool 15. The movement ofcarriage 34 is preferably controlled via computer.

[0033] During the winding of the fiber onto spool 15, a constant torqueis applied to the dancer pivot arm 32 in a direction which is opposite,or away from, first pulley 30 a. Such a torque may be provide, forexample, via a hydraulic air cylinder attached to dancer pivot arm 32.The torque applied to dancer pivot arm 32 and the speed with which thespool is rotated are controlled so as to wind the fiber onto the spoolwith a uniform winding tension applied to the fiber.

[0034] The angular position of dancer arm 32 is monitored and employedin conjunction with a control computer to control the rotating take upspeed of the spool 15. A sensor senses the angular position of thesecond pulley 30 b. In a preferred embodiment, the sensor is an RVDT.The position of the second or dancer pulley 30 b is used to determinethe difference between the speed at which the optical fiber is beingsupplied from screener section 12 and the speed at which the opticalfiber is being wound on a spool. The speed at which the spool 15 isrotating can then be adjusted according to the speed of the opticalfiber being supplied from screener section 12, so that the fiber iswound under the spool 15 with a uniform amount of tension. The verticalposition of the second pulley 30 b is also used to detect a break in theoptical fiber, as the load cell attached to the second pulley 30 b willregister zero load when the optical fiber breaks.

[0035] As illustrated in FIG. 1, winder section 14 includes twoindependent spindles which each retain a take up spool 15. The spindlesare mounted 180 degrees apart on an indexing turret 40. Winding of fiberonly occurs to the spindle that is in the upper position. The lowerposition is used to hold an empty spool that is ready in the event of afiber break.

[0036] The breaks that occur during a fiber draw operation can be brokendown into two basic categories, pre-screener breaks, which are breaksthat occur in the fiber before the fiber has reached the screenercapstan 24, and post-screener breaks, which are breaks that occur in thefiber after the fiber has passed the screener capstan 24. By monitoringthe load cells attached to turnaround pulley 20 and the position ofdancer arm 32, the control computer can control operation of the windingsystem and react to breaks which occur at various points in the windingoperation. For example, when a pre-screener break occurs, the load cellon turnaround pulley 22 will almost immediately register zero load.Consequently, when the computer senses that the load at turnaroundpulley is zero, the computer initiates a control sequence forrethreading of the fiber through the screener capstan as well as theremainder of the winding system.

[0037] In a preferred embodiment of the invention, several simultaneousfiber threading actions occur at the screening section and at thewinding section of the machine when a pre-screener break is detected.The actions at the screener section will be described first, followed bythe winder section description.

[0038] Threading of the Screener Section:

[0039] In normal operational mode, while fiber is being drawn and woundonto spool 15, the nozzle of aspirator 16 is positioned adjacent thefiber path as it exits tractor capstan 20 traveling toward windersection 14. When a fiber break occurs between the tractor and screenercapstan, the fiber down stream of the break is pulled through the fourremaining process pulleys downstream and onto the take up spool. Thecomputer immediately detects the fiber break via the turnaround pulleyload cell, registering zero load. With nothing to guide it, fiberexiting the tractor capstan is pushed out from the capstan in a straightline. Aspirator 16 may be positioned such that the fiber streaming fromthe tractor capstan will be sucked into the nozzle of the aspirator 16,as illustrated in FIG. 4A. Alternatively, aspirator 16 can be positionedat a location which is remote from the path of the fiber, and after afiber break occurs, the aspirator can be moved into a position in whichit collects the fiber.

[0040] High pressure air is supplied to the aspirator 16 from anelectronically controlled proportional air valve, and the pressure toaspirator 16 creates a vacuum at the aspirator nozzle, and the vacuumpulls the fiber into the aspirator 16. The fiber exits the aspiratorinto a fiber collection can. The amount of time between a prescreenerbreak and acquisition of the fiber by the aspirator is only a fractionof a second due to the fact that the aspirator is positioned nearly inline with the path of the fiber during normal winding operation. Ofcourse, the aspirator could be positioned further away from the path ofthe incoming fiber and the aspirator vacuum increased until such time asthe fiber is captured by the aspirator.

[0041] Consequently, almost immediately after a prescreener breakoccurs, the fiber is being sucked into aspirator 16. The aspirator isthen moved in accordance with the invention to facilitate rethreading ofthe fiber through the screener capstan. As illustrated in FIG. 1, theaspirator is movable along three motorized linear axes 17, 18 and 19(and thereby is movable in three dimensions) to facilitate threading ofthe entire machine.

[0042] The screener capstan rethreading sequence is illustrated withreference to FIGS. 1 and 4A-4E. It should be noted that FIGS. 4A-4E areonly schematic, and actual relative dimensions have been altered tofacilitate illustrations of the invention. Once fiber 8 is acquired byaspirator 16, a rethreading sequence is initiated to rethread theturnaround pulley 22 and the screener capstan 24. To accomplish this,the aspirator may be positioned or moved to be positioned essentially inline with fiber exiting the tractor capstan, as illustrated in FIG. 4A,so that the aspirator begins to collect the fiber exiting the capstan24. The aspirator is then moved along transverse support member 18 toguide the fiber onto the groove of turnaround pulley 22 and wrap thefiber around 90 degrees of turnaround pulley 22, as illustrated in FIG.4B. Threading of the final 90 degrees of turnaround pulley 22 and thescreener capstan is preferably done using a guide finger system 44, asshown in FIG. 2. Guide finger system 44 consists of at least one, andpreferably a pair of guide fingers 45 a and 45 b. These finger-likeguide fingers do not grasp the fiber, but rather enable the fiber toslide around their outer periphery and into the aspirator, where it iscontinuously discarded. This process facilitates rethreading of thefiber while the fiber continues to be drawn during the fiber drawoperation. The guide fingers may be for example, a pair of cylindricalmetal tubes which may or may not be rotatable around their axis tofacility transport of the fiber over the surface of the guide fingers.The guide fingers are moved up and down via Z-axis support bars 46 andback and forward (left and right) along X-axis support member 47, bypneumatic slides. The second guide finger 45 b also has a pneumaticslide 48 that allows motion in and out (Y axis). The guide fingers 45 aand 45 b are in the Z-up, X-forward (toward the winder section), andY-in position, as illustrated in FIG. 2, prior to the initiation of therethreading sequence. Once the aspirator has threaded 90 degrees ofturnaround pulley 22, the guide fingers are moved to the Z down positionso that both guide fingers are behind the line of fiber going into theaspirator from the turnaround pulley, as illustrated in FIG. 4B.

[0043] The guide fingers 45 a and 45 b are then moved toward the X-back(away from the winder section) position so that threading of thescreener capstan can take place. As the guide fingers 45 a and 45 b aremoved in this manner, guide finger 45 a engages fiber 8 and moves ittoward screener capstan 24. At the same time, guide fingers 45 a and 45b are moving to rethread the screener capstan 24, aspirator 16 beginsmoving toward the winder section 14 to begin rethreading of windersection 14, as illustrated in FIG. 4C. This action allows for fasterrethreading of the entire system as two portions of the machine, thescreener section 12 and the winder section 14, are being threadedsimultaneously. Guide fingers 45 a and 45 b continue until first guidefinger 45 a is adjacent screener capstan 24, at which point the fiberpath is almost 180 degrees around turnaround pulley 22, 180 degreesaround first guide finger 45 a, and into the aspirator which is stillmoving to a position behind the fiber take up spool 15 as illustrated inFIG. 4D. At this point, the second guide finger 45 b moves to the Y-outposition i.e., toward screener capstan 24, as illustrated in FIG. 4E.Guide finger 45 b urges the fiber into the area of the screener capstanwhere the belt and the capstan meet. The screener capstan may also beprovided with one or more nubs or snagger hooks that are positioned onthe outer diameter of the capstan. As the capstan rotates, the nubs canhelp urge the fiber into the area where the belt and capstan meet. Oncethe fiber is captured between the belt and capstan, the fiber is carriedaround the capstan, below and out of engagement with the first guidefinger 45 a as it is carried around the screener capstan. At this pointguide finger 45 b retracts, and the threading of screener section 12 iscomplete, with the fiber traveling around turnaround pulley 22 andscreener capstan 24. The result is that the turnaround pulley 22 andscreener capstan 24 are threaded without breaking the line of fiber,which is traveling into the aspirator. Guide fingers 45 a and 45 b arethen returned to the Y-in, Z-up, and X-forward positions.

[0044] Threading of the Winder Section

[0045] Threading of the winder section 14 preferably takes placesimultaneous with the threading of the screener section 12. Thus,referring to FIG. 3, when a pre-screener break is detected by theturnaround pulley 22 load cell, the first actions of winder section 14occur simultaneously to facilitate threading of the winding section bythe aspirator. In FIG. 3, a pair of rotatable fiber storage spools 15are mounted 180 degrees apart on turret 40. In the embodimentillustrated, only one of the spools 15 is visible, and is collectingfiber being supplied via the fiber draw process. The other fiber storagespool 15 is positioned 180 degrees, or directly underneath the spool 15which is visible. The other spool 15 is empty and ready to be moved intoposition to receive fiber from the fiber draw process. Also visible inFIG. 3 is dancer platform 56, upon which dancer pulley 32 is mounted.Dancer platform 56 is movable along a transverse slide (not shown), fromthe closed position illustrated, in which dancer pulley 32 is engagingfiber 8 and forcing fiber 8 to take a serpentine path, to an openposition, in which dancer pulley 32 is moved and positioned on the otherside of the path of fiber 8. In FIG. 3, dancer pulley 32 is shown in theclosed position. Likewise, pulley 30 c is mounted on a traverse (notshown), which is capable of moving pulley 30 c into and out of engagingposition with the path of fiber 8. As mentioned above, while the guidefingers 45 a and 45 b are moving the fiber 8 toward screener capstan 24to thread the screener 24, aspirator 16 and thus fiber 8 aresimultaneously moved toward the winding section 14. At the same time,three things preferably occur simultaneously:

[0046] (1) the winder turret 40 indexes 180 degrees so that a new emptyfiber storage spool 15 is in place for winding;

[0047] (2) the new spool 15 begins rotating slightly faster than thelinear speed of the incoming fiber; and

[0048] (3) the pulley 30 a, dancer pulley 30 b and pulley 30 c are movedon their respective traverse slides into an open position (as shown inFIG. 5a) to enable threading of the fiber 8 through winder section 14.For this to occur pulley 30 c is moved along its own pneumatic slidetoward a position outboard of the fiber path.

[0049] The dancer stops 33 come together to hold the dancer arm 32 in afixed position, and the dancer slide (not shown) moves the dancerplatform 34 toward the inboard position of the path to be taken by thefiber. Pulley 30 a is moved along pneumatic slide 57 to a positionoutboard of the path to be taken by the fiber.

[0050] As can be seen in FIG. 3, the winder section was designed so thatthe aspirator 16 can pass freely above all of the winder componentswhile fiber is being pulled into the aspirator nozzle. The aspirator 16moves to a position that is above and behind the take up spool 15.Aspirator 15 then moves downward, guiding the fiber 8 onto the fourthprocess pulley 30 d. The aspirator continues moving down until the lineof fiber coming from pulley #4 is tangent to the barrel of the take upspool. At this point the winding section is as illustrated in FIG. 5a.

[0051] When the aspirator has threaded fiber 8 onto the pulley 30 d andthe fiber is tangent to the barrel of the spool 15, pulleys 30 a, 30 b,and 30 c are moved to their normal run position. Thus, as illustrated inFIG. 5b, pulleys 30 a and 30 b move into contact with the fiber. Thedancer slide then moves the dancer pulley 30 b toward a position whichis outboard of the path of the fiber. This action brings the fiber pathto its normal running position illustrated in FIG. 5b, namely,approximately 90 degrees around pulley 30 a, 180 degrees around pulley30 b, 90 degrees around pulley 30 c and approximately 15 degrees aroundpulley 30 d. The dancer stops are moved to their run position and thedancer is forced to the outboard stop.

[0052] Spool 15 is then traversed to bring the fiber into contact with asnagger tooth 58, which is present on the flange of spool 15. The fiberis wedged into the snagger and cut, separating the fiber from theaspirator and beginning the winding of the fiber onto spool 15. Thedancer is initially pulled toward the inboard position of the winder dueto the over spinning of the take up spool. The speed of the rotation ofthe take up spool 15 may be controlled by the dancer position and thespeed adjusted so that the dancer arm is pulled to a nominal runningposition. The aspirator then moves back to the staged position, which isproximate to in line with the fiber exiting the tractor capstan.

[0053] The spool that was taking up fiber before the break isautomatically unloaded from the bottom of the winder turret 40, and anew empty spool is loaded into the spindle. The machine is then readyfor the next fiber break event.

[0054] Cases also exist where the fiber is broken somewhere between thescreener capstan and the take up spool. The first case may be when thetake up spool is full. A second case occurs when the fiber is detectedthat is out of specification (e.g. the diameter is too large or toosmall). In either of these two cases, an automatic fiber cutter 36intentionally cuts the fiber. Such a mechanical cutting device may bepositioned, for example, just before the fiber enters the first processpulley 30 a. A third case of a post screener break occur when somethingunexpected causes the fiber-to break (stray fiber, nicked processpulley, etc. . . . ) after the screener capstan 24.

[0055] The only difference in the threading sequence between a postscreener break and a pre-screener break is that the screener sectiondoes not need to be rethreaded. In the case of a post screener break,the fiber is carried out of the screener capstan in a straight line. Theaspirator is moved to a position adjacent the screener capstan so thatthe fiber can be captured by its vacuum. Once captured, the machine goesthrough the winder section threading sequences described above, as if itwere a screener break, except that no actions need be performed tothread the screener capstan since it is still threaded.

[0056] A control system for controlling the winding apparatus 10 toperform the abovementioned threading and winding operations ispreferably also provided. The control system preferably includes aprogrammable logic controller to control the operation of the varioussequence of events, monitor all of the sensors (e.g., the load cell onturnaround pulley 20 and the load applied by the fiber to dancer 34).The logic controller may also be used to control air cylinders which areused to move various components (e.g. pulleys 30 a-30 c) into position,as well as to communicate with a motion control computer. The motioncontrol computer preferably controls and monitors the moving mechanismssuch as aspirator 16, guide fingers 45A and 45 b.

[0057] It will be apparent to those skilled in the art that variousmodifications and variations can be made to the present inventionwithout departing from the spirit and scope of the invention. Thus, itis intended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

What is claimed is:
 1. A method of screening an optical fiber during afiber draw process, comprising pulling a length of optical fiber from anoptical fiber preform at a fiber draw speed greater than 20 m/s,imparting a desired tensile stress to said fiber to thereby test thestrength of said fiber and subsequent to said imparting a tensilestress, winding said fiber onto a spool.
 2. The method of claim 1,wherein said desired tensile stress is greater than about 80 psi.
 3. Themethod of claim 1, wherein said desired tensile stress is greater thanabout 95 psi.
 4. The method of claim 1, wherein said spool is a shippingspool to be shipped to a customer, and said fiber is wound onto saidshipping spool.
 5. The method of claim 4, further comprising, shippingsaid shipping spool with said fiber thereon to a customer.
 6. The methodof claim 2, wherein said fiber is wound onto a spool which enablesaccess to both ends of said fiber on said spool.
 7. The method of claim2, wherein said fiber is wound onto said shipping spool in a mannerwhich enables both ends of said fiber to be accessed while said fiber isstored on said spool.
 8. The method of claim 4, wherein said fiber iswound onto said shipping spool in a manner which enables both ends ofsaid fiber to be accessed while said fiber is stored on said spool. 9.The method of claim 5, wherein said method further comprising, prior tosaid shipping, conducting tests on said fiber while said fiber is onsaid spool.
 10. The method of claim 9, wherein said tests include atleast one test selected from the group consisting of optical time domainreflectometry, dispersion geometry and polarization mode dispersion. 11.The method of claim 2, further comprising conducting at least oneoptical property test on said fiber while said fiber is on said shippingspool by a testing method which involves connecting one end of saidfiber on said spool to a light source, and evaluating the light at theother end of the fiber.
 12. The method of claim 9, further comprisingconducting at least one optical property test on said fiber while saidfiber is on said shipping spool by a testing method which involvesconnecting one end of said fiber on said spool to a light source, andevaluating the light at the other end of the fiber.
 13. The method ofclaim 1, wherein said imparting a tensile stress comprises feeding saidfiber through a screener capstan which works in conjunction with anothercapstan which is in contact with said fiber to impart said desiredtensile stress to said fiber during said draw process, and said screenercapstan is rotated at a higher circumferential speed than said othercapstan to thereby impart said desired tensile stress.
 14. The method ofclaim 13, further comprising monitoring the tension in the fiber in saiddraw process and adjusting the speed of said screener capstan inresponse to said monitored tension, to thereby maintain said tensilestress.
 15. The method of claim 14, wherein said monitoring stepcomprises monitoring said tension via a load cell operatively connectedto said fiber.
 16. The method of claim 15, wherein said load cell isconnected to a pulley which in turn contacts said fiber, said fibercontact causing said pulley to rotate
 17. The method of claim 15,wherein a computer monitors said tension in said fiber via said loadcell.
 18. The method of claim 4, wherein less than 150 km of fiber iswound onto said spool.
 19. The method of claim 4, wherein a length offiber is wound onto said spool which is sufficiently short to enable theattenuation of said fiber to be measured while said fiber is on saidspool.
 20. A method of screening an optical fiber during a fiber drawprocess, comprising pulling a length of optical fiber from an opticalfiber preform, imparting a desired tensile stress to said fiber tothereby test the strength of said fiber and subsequent to said impartinga desired tensile stress, winding said fiber onto a spool which is to beshipped to a customer or optical fiber cabling operation with said fiberthereon.
 21. The method of claim 20, wherein said desired tensile stressis greater than about 80 psi.
 22. The method of claim 20, wherein saiddesired tensile stress is greater than about 95 psi.
 23. The method ofclaim 20, further comprising shipping said spool with said fiber thereonto a customer.
 24. The method of claim 20, wherein said fiber is woundonto said spool in a manner which enables access to both ends of saidfiber while said fiber is stored on said spool.
 25. The method of claim23, wherein said fiber is wound onto said shipping spool in a mannerwhich enables both ends of said fiber to be accessed while said fiber isstored on said spool.
 26. The method of claim 20, wherein said fiber iswound onto said shipping spool in a manner which enables both ends ofsaid fiber to be accessed while said fiber is stored on said spool. 27.The method of claim 26, wherein said method further comprising, prior tosaid shipping, conducting tests on said fiber while said fiber is onsaid spool.
 28. The method of claim 26, wherein said method furthercomprising, prior to said shipping, conducting tests on said fiber whilesaid fiber is on said spool.
 29. The method of claim 28, wherein saidtests include at least one test selected form the group consisting ofoptical time domain reflectometry, dispersion geometry and polarizationmode dispersion.
 30. The method of claim 28, further comprisingconducting at least one optical property test on said fiber while saidfiber is on said shipping spool by a testing method which involvesconnecting one end of said fiber on said spool to a light source,launching light from said light source through said fiber, andevaluating said launched light at the other end of said fiber.
 31. Themethod of claim 20, wherein said imparting a tensile stress comprisesfeeding said fiber through a screener capstan which works in conjunctionwith another capstan which is in contact with said fiber to impart saiddesired tensile stress to said fiber during said draw process, and saidscreener capstan is rotated at a higher circumferential speed than saidother capstan to thereby impart said desired tensile stress.
 32. Themethod of claim 31, further comprising monitoring the tension in thefiber in said draw process and adjusting the speed of said screenercapstan in response to said monitored tension, to thereby maintain saidtensile stress.
 33. The method of claim 32, wherein said monitoring stepcomprises monitoring said tension via a load cell operatively connectedto said fiber.
 34. The method of claim 33, wherein said load cell isconnected to a pulley which in turn contacts said fiber, said fibercontact causing said pulley to rotate
 35. The method of claim 34,wherein a computer monitors said tension in said fiber via said loadcell.
 36. The method of claim 20, wherein no more than 100 km of fiberis wound onto said spool.
 37. The method of claim 20, wherein a lengthof fiber is wound onto said spool which is sufficiently short to enablethe attenuation of said fiber to be measured while said fiber is on saidspool.
 38. A method of threading a moving length of fiber through acomponent in a fiber draw, fiber winding or fiber testing process,comprising: activating an aspirator to obtain said fiber at a firstlocation and moving said aspirator in at least two dimensions to movesaid fiber to a second location to thread said fiber through a componentin said fiber draw process.
 39. The method of claim 38, wherein saidmoving length of fiber is a moving length of fiber in a fiber drawprocess, and said method further comprises orienting at least a first,second, and third pulley so that, when said aspirator moves said fiberto said second location, said pulleys are disposed along the length ofsaid fiber and on alternating sides of said desired fiber, and saidmethod further comprises moving said second pulley across the path ofsaid fiber to retain said fiber in contact with said first, second, andthird pulleys, thereby causing said fiber to move in a serpentine path.40. The method of claim 38, wherein said aspirator is moved to guidesaid fiber onto at least one guide pulley by said aspirator guiding saidfiber between or against a pair of surfaces which are disposed on eachside of said guide pulley, said surfaces sloping toward said guidepulley to thereby guide said fiber onto said guide pulley.
 41. Themethod of claim 39, wherein said aspirator is moved to guide said fiberonto at least one guide pulley by said aspirator guiding said fiberbetween or against a pair of surfaces which are disposed on each side ofsaid guide pulley, said surfaces sloping toward said guide pulley tothereby guide said fiber onto said guide pulley.
 42. The method of claim38, wherein said second location is proximate to a fiber winding spool.43. The method of claim 42, further comprising engaging said fiber at apoint along said fiber which is between the aspirator and the source offiber, and winding said engaged fiber onto said spool.
 44. The method ofclaim 43, wherein said engaging said fiber comprises engaging said fiberby a snagger tooth which is located on said spool
 45. The method ofclaim 38, further comprising engaging said fiber at a point along thelength of said fiber which is between the source of said fiber and saidaspirator, and moving said engaged fiber to facilitate threading of saidfiber through said at least one component of said fiber draw process.46. The method of claim 45, wherein said engaging a fiber step comprisesengaging a moving length of fiber, moving said engaged length of movingfiber into contact with a capstan to thereby thread said fiber aroundsaid capstan.
 47. The method of claim 46, wherein simultaneous with saidthreading of said capstan, said aspirator is moving to said secondlocation, and said second location is proximate to a winding spool. 48.The method of claim 47, wherein said moving length of fiber is a movinglength of fiber in a fiber draw process, and said method furthercomprises orienting at least a first, second, and third pulley so that,when said aspirator moves said fiber to said second location, saidpulleys are disposed along the length of said fiber and on alternatingsides of said desired fiber, and said method further comprises movingsaid second pulley across the path of said fiber to retain said fiber incontact with said first, second, and third pulleys, thereby causing saidfiber to move in a serpentine path.
 49. The method of claim 48, furthercomprising moving said aspirator to guide said fiber onto at least oneguide pulley by said aspirator guiding said fiber between or against apair of surfaces which are disposed on each side of said guide pulley,said surfaces sloping toward said guide pulley to thereby guide saidfiber onto said guide pulley.
 50. An apparatus for drawing and windingfiber onto a spool, and prooftesting the fiber after drawing of thefiber but prior to the fiber being wound onto the spool, comprising: afurnace for softening an optical fiber preform sufficiently that a fibercan be drawn therefrom; a tractor device capable of drawing fiber fromsaid preform at a rate exceeding 20 m/s; a prooftesting devicecomprising a first tractor assembly downstream of said furnace includingat least one wheel and a motor for driving said wheel at a firstcircumferential speed a second tractor assembly including at least onewheel and a servo motor for driving said wheel at a secondcircumferential speed the difference between said first and secondcircumferential speeds creating a desired proof testing tensile stress;a load cell operatively connected to the fiber for monitoring tension insaid fiber; and a computer control for receiving input from the loadcell and adjusting the speed of the first or second tractor assembliesto aid in maintaining uniform tensile stress.
 51. Apparatus of claim 50,wherein said second circumferential speed is faster than the firstcircumferential speed.
 52. A method of changing optical fiber storagespools in an optical fiber winding process, comprising: cutting thefiber being fed from a fiber supply source after a first fiber storagespool has received a desired amount of optical fiber; capturing thefiber being supplied from said fiber supply source in an aspirator; andmoving said aspirator and a second fiber storage spool with respect toone another to rethread the fiber onto said second fiber storage spool.53. The method of claim 52, wherein said fiber supply source is a movinglength of fiber in a fiber draw operation.
 54. The method of claim 52,wherein a snagger tooth on said second storage spool snags said fiberonto said second storage spool.
 55. The method of claim 52, wherein saidaspirator is moved in at least two dimensions to wind said fiber ontosaid second storage spool.
 56. A method of exposing optical fiber to atensile screening test comprising: feeding said fiber through a tensilescreening tester which is located in the path of a moving length ofoptical fiber, said length of optical fiber being drawn from an opticalfiber preform, said tensile screening tester located between saidpreform and a storage spool for collecting said length of fiber, whereinthe tension in said fiber being drawn from said preform is monitored andthe tension being applied to said fiber via said fiber tensile tester isadjusted in response to fluctuations in said incoming fiber tension. 57.In a process for winding a length of fiber being drawn in an opticalfiber preform in a fiber draw process onto at least one storage spool,the improvement comprising, after the length of fiber has begun to bestored on said at least one storage spool, identifying fiber which isout of specification and removing said out of specification fiber fromthe source of fiber before the fiber is wound onto said at least onestorage spool.
 58. The method of claim 57, wherein said method compriseswinding said length of fiber onto a first storage spool, and said methodfurther comprises cutting and removing a portion of said length offiber, and rewinding at least a portion of the remainder of said lengthof said fiber onto a second storage spool.